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Creation 40(4):56, October 2018

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Salad-eating sharks


wrangel/123rf, Joseph Belanger/123rfsalad-eating-shark

Sharks are widely regarded as carnivores (meat-eaters), and until recently the bonnethead shark, Sphyrna tiburo, was no exception. Living in shallow waters close to shore, it was known to hunt in the seagrass meadows for fish, crabs, and shrimp.

However, analysis of the stomach contents of these sharks revealed they were also eating copious amounts of seagrass—especially the juvenile sharks, with up to 62% of their total gut contents identified as plant material.

Unsure whether seagrass-eating was incidental or deliberate, and dubious as to whether the bonnethead sharks could extract any nutritional benefit from it given their too-short (for digesting plant fibrous material) “carnivorous ancestry” intestines, researchers investigated further.1 For three weeks they fed captive bonnethead sharks a daily diet of 90% seagrass (containing a traceable 13C label) and 10% squid. The sharks all gained weight, and more than half of the seagrass was being successfully digested. Furthermore, the researchers observed a spike in the activity of a cellulose-degrading enzyme—possibly belonging to a helpful microbe living in the shark’s gut.

The researchers say these results provide explicit evidence that bonnethead sharks, “animals previously thought to be solely carnivorous”, derive substantial nutritional benefit from eating seagrass.1

Reporting the discovery, Science journal described the bonnethead shark as “the world’s first salad-eating shark”.2 Some might dispute that given longstanding observations in the wild of nurse sharks grazing algae. And also due to the existence of ‘Florence’, a captive nurse shark that since an earlier fishhook injury now shuns meat in favour of broccoli, cabbage, and other greens.3,4

Actually, none of these should be considered the world’s first salad-eating sharks. That honour goes to the first sharks that ever lived, created about 6,000 years ago on Day 5 of Creation Week, and created 100% vegetarian. Today’s salad-eating sharks are a reminder that theirs was originally a herbivorous ancestry, not a carnivorous one, even though in today’s post-Fall world they and other ‘vegetarian carnivores’ might need to augment their diet with some meaty protein from time to time.

References and notes

  1. Leigh, S., Papastamatiou, Y., and German, D., Omnivorous sharks? An analysis of bonnethead shark digestive physiology provides evidence for seagrass digestion and assimilation, sicb.org, Society for Integrative and Comparative Biology—Annual Meeting 2018, Abstract 109-1, 7 January 2018. Return to text.
  2. Pennisi, E., Meet the world’s first salad-eating shark, sciencemag.org, 7 January 2018 | doi:10.1126/science.aas9301. Return to text.
  3. Wrenn, E., Meet Florence, the world’s first vegetarian shark who prefers celery sticks and cucumber to fish, dailymail.co.uk, 18 May 2012. Return to text.
  4. Catchpoole, D., Vegetarian shark—The nurse shark that uses her razor-sharp, serrated teeth to pulp broccoli and cabbage, celery and lettuce, Creation 36(2):15, 2014. Return to text.

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Readers’ comments

Courtney K.
Wildflower Magazine 2019 | Volume 36(2) says something very interesting relating to this, but especially regarding humanity's impact on the environment, from a Native American:

He sees all that nature provides as proof of “the unconditional love the Creator has for us.” But, he adds, ”Some of us didn’t take care of it. Some of us abused it. That’s where we are with Mother Earth today.”

I find it interesting how close he came to your articles on the environment. With the right amount of resources, animals originally may have been vegetarian, but a combination of the aftereffects of the flood, depleted resources, greed, etc. had and have been forcing animals to eat meat when necessary. Over time, with meat the majority available, maybe the ability to get nutrition adequately and the behavior of seeking out plants has partly mutated away from animals and other organisms, so even if animals got back to going vegetarian, their mutations would have gone partly away because they hadn't used them (natural selection). But wherever carnivores exist, I wonder just how recently they went carnivore/omnivore, and whether there is an example of an animal, basically the same, but living on opposite sides of the world, yet one is vegetarian and one is a carnivore. Like, a monkey, for instance. I wonder what kinds of animals will tend to favor meat? Is it the teeth? The size? Most large cats (except for a few lions in special cases like in some articles here) prefer meat; bears are omnivores; I wonder it is simply harder for some animals (sheep, deer) to be able to eat meat for some reason? Or whether there is something about them that makes vegetarianism with little available still possible, versus other kinds of animals/plants, etc.
Jonathan Sarfati
Some fair questions, and some are answered in the related articles. Note that while God allowed human carnivory after the Flood, and this has never been rescinded, animal carnivory happened after the Fall, and clearly before the Flood.

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